Taste and odor removal from organic compounds



?atented @et. 3Q, 1M5

attain I was stares tartar praise TASTE AND ODOR REMOVAL FROM ORGANIC COMPOUNDS Harry 0. Hetherlngton, Charleston, W. Va... as-

signor to E. I. du Pont de Nemours & Uompany, Wilmington, DeL, a corporation of Delaware No Drawing. Application March 28, 1942, Serial N0. 436,712

4 Claims. (01. zoo-611.5)

This invention relates to the processing of organic compounds and more particularly procreaction mixture containing such acids.

essing of such compounds to render them free which ordinarily is required when processing is carried out in vessels constructed of other metals. Certain processes, however, although they are conducted in the presence of only mildly acidic reactants could not be carried out in the alloy steel vessels without imparting odor or taste to the product and in some instances much time consuming and costly clean-up processes were necessary to give acceptable finished products.

An object of the present invention is to provide a process for the treatment of organic compounds in alloy steel to give stable products free from contaminating taste and odor. Another object is to provide a process for the treatment of mildly corrosive organic compounds, or solutions of such nature, in high chromium-alloy steel vessels whereby the products are obtained free from foreign taste and odor. Yet another object is to provide a process for the preparation of organic compounds free from foreign odor or taste which compounds are processed in stainless steel vessels while in the presence of inorganic acids such as sulfuric acid, hydrochloric acid, and the like by efiecting-the process in the presence of polyvalent metals. Other objects and advantages of the invention will hereinafter appear.

It has been found that liquids can be processed and/or stored in alloy steel vessels and foreign taste and odor avoided even though the products or the reactants from which they are formed are corrosive provided the processing and/or storage in said vessels is conducted in the presence of polyvalent metalssuch, for example, as manganese, bismuth, cobalt, iron, or especially copper.

The advantageous result is particularly marked for reactions in which organic or inorganic acids are present, such as sulfuric, hydrochloric, oxalic, benzoic, acetic, propionic, tartaric, hydroxyacetic acids, etc., as reactants or catalysts or are present during'the recovery of the product from the In the preparation of (methoxymethoxy) ethanol from methylal and ethylene glycol, sulfuric acid is used as the catalyst. (Methoxymethoxy) ethanol. is recovered directly by distillation from the reaction-product and inasmuch as this compound is used where odors would be objectionable, the distillation is conducted in an alloy steel still. If no polyvalent metal is present the product picks up undesirable odors during the distillation while if there is present 0.0002% or more of a polyvalent metal such as those given, above or equivalent concentrations of salts thereof, such as sulfate, acid sulfate, phosphate, chloride, acetate, hydroxy-acetate, or the like, the '(methoxymethoxy) ethanol is recovered substantially free from foreign odors. Foreign odor and taste can be avoided in organic liquids generally by this method, and it is intended that the term liquids include compounds which may be solids under normal conditions of temperature and pressure but which are proc- For example, in this category are included hydroxyacetic acid and its esters, glycolides, tartaric acid and its esters, citric acidand the like.

The alloy steels referred to in this specification include particularly those which contain a high percentage of chromium, i. e. up to in the order of 30% chromium. For example, the well-known alloy steel containing 18% chromium, 8% nickel, and the remainder mostly iron with traces of carbon, manganese, sulfur, etc., is extensively used as a material for the construction of reactant vessels; as well as steels containing as their major constituent, other than iron, from 12 to 14% chromium. Said alloy steels are especially adapted for use in accord with the invention.

The wide applicability of this method will be appreciated from the following processes in which it has been found to be very effective.

Example 1.I.n the preparation of dimethoxyethyl adipateQa mixture containing adipic acid, ethylene glycol monomethyl ether, and sulfuric acid was processed in an alloy steel reaction still kettle having a composition of approximately chromium 18%, molybdenum 2%, nickel 8%. There was recovered from the reaction mixture a wholly unacceptable product with a sulfurous acid odor. This odor was completely eliminated byintroducing 0.0075% of copper as CuSo4.5HzO into the reaction mixture prior to the reaction.

Similarly the sulfurous odor contaminating diisobutyl adipate, dicyclohexyl adipate, and dicarbamate 0.003% of copper as basic copper carbonate was added to a mixture consistingof 1047 parts of isobutanol and 156 parts of urea. The mixture was heated for several hours at a temperature above 150 C. in a stainless steel apparatus of which some of the internal surfaces were of the approximate composition given in previous examples and others of similar chromium and nickelcomposition but containing no molybdenum. The product, following removal of unreacted isobutanol and urea, was entirely free of the objectionable foreign odor which it acquires during its preparation in the absence of copper.

Example 4.A mixture containing 354.6 parts of ethylene glycol, 311.6 parts of a methylalmethanol azeotrope (containing 92% methylal),

two parts sulfuric acid, and 0.0075% copper which was added as copper sulfate, was refluxed for six hours in a stainless steel still, the kettle of which was of 18 Cr-8 Ni2 Mo composition and the heating coils, column and other parts of unmodified 18-8 composition. The reaction product was then distilled, yielding a (methoxymethoxy) ethanol (CHsOCHzOCHaCI-IaOI-I) fraction which was not only free from foreign taste and odor but which in addition was thermally stable. In the absence of the copper the product was thermally unstable and possessed a highly objectionable odor. I

Example 5.In the preparation of hydroxyacetic acid 780v parts of methyl hydroxyacetate was hydrolyzed with 320 parts of water in the presence'of 0.0016 part of copper. This hydrolysis, the removal of methanol by distillation, the subsequent concentrating of the aqueous solution and the final flash evaporation of remaining free water were all effected in stainless steel equipmentof the approximate 18 chrome 8 nickel type. The crystalline hydroxyacetic acid obtained was entirely free of the objectionable odor which had characterized this product when made under similar conditions but in the absence of copper.

I claim:

1. A method of inhibiting the development of foreign taste and odor in (methoxymethoxy) ethanol and of stabilizing the (methoxymethoxy) ethanol, the step which comprises preparing the (methoxymethoxy) ethanol, from ethylene glycol and a methylal-methanol azeotrope using sulfuric acid as the catalyst, in an 18% chromium- 8% nickel alloy steel vessel, there being present during the reaction at least 0.0002% copper based on the weight of (methoxymethoxy) ethanol.

2. Stabilized (methoxymethoxy) ethanol substantially free from foreign taste and odor containing from .0002 to .02% copper.

3. (Methoxymethoxy) ethanol stored in contact with chrome-alloy steel and inhibited against the development of taste and odor by the presence of from 0.0002 to 0.02% copper as copper sulfate.

4. A method of inhibiting the development of foreign taste and odor in (methoxymethoxy) ethanol resulting from contact with chromealloy steels, the step which comprises inhibiting the development of taste and odor in the (methoxymethoxy) ethanol, while in contact with chrome-alloy steel, by incorporating therein at least 0.0003% of copper ions based on the Weight of the (methoxymethoxy) ethanol.

HARRY C. HETHERINGTON. 

